removelast

void removeLast(Deque *queue){
    if(!isEmpty(queue)) {
        if(!(queue->tail)->next) // in case of last element in the queue
            reset(queue);
        else{
            Node *node = (queue->head)->back;
            node->next = NULL;
            free(queue->head);
            queue->head = node;
        }
    }
}